Process of forming pneumatic tubes



Au 24, 1926. I 1,597,658

- I W. L. FAIRCHILD PROCESS OF FORMING PNEUMATIC TUBESL Filed Sept. 2, 1925 7 INVENTOR [5 W44 75/? L. BURCH/L0 Y I AZ ORNEY Patented Aug. 24, 1926.

UNITED STATES 1,597,658 PATIENT OFFICE.

wan'rnn L. mmonnm, on NEW roux, N. Y.

rnocnss or romaine PNEUMATIC TUBES.

Application filed September 2, 1925. Serial No. 54,053.

This invention relates to a new and improved method of producing hollow rubber articles, such as pneumatic tubes for vehicle tires and the like.

One of the objects of the invention is to provide a new and improved method of producing a pneumatic tube wherein the cost of production'is reduced to a minimum.

Another object of the invention is to provide a new and improved process of vulcanizing a raw rubber tube, wherein there is produced a tube without seams, and a tube wherein all the material of the tube is thoroughly vulcanized.

A further object of the invention is to provide a new and improved method of the above character, which may be carried on more expeditiously than it has been possible to carry on viileanizing operations on pneumatic tubes and the like according to practices hitherto pursued.

,Other objects and aims of the invention more or less specific than those referred to above, will be in part obvious and in part pointed out in the course of the following description of the steps and the relation of each step to one or more of the others thereof employed in carrying out my process, and the scope of protection contemplated will be indicated in the appended elalms.

In the accompanying drawings wherein I have shown sehematicall a preferred embodiment of my improve method adapted for use in producing pneumatic tubes:

Figure 1 is a plan view of a tube of raw rubber, which is of suitable length to be formed into a pneumatic tube.

Figure 2 is a similar view of the tube, showing the ends united, with the valve stem inserted in place.

Figure 3 is a sectional view showing a preferred form of apparatus adapted for use in carryin out my improved process, also showing the pneumatic tube mounted in the mold, when the first step of my improved method has been carried on in connection with said tube.

Figure 4 is a sectional view through a portion of the mold, showing the tube mounted therein ,when the second step of my improved method has been performed.

Figure 5 is a sectional view showin the valve 'llustrated in Figure 3, in a di erent positi n.

re 6 is. a view of said valve in the position shown in Figure 1, to which position it has been moved, after the operation shown in Figure 4 has been carried out.

Figure 7 is a sectional view similar to Figure 4, showing the tube in the closed mold, after a third step of the. operation of my improved method has been carried out. Figure 8 .is a view of the valve shown in Figures 3, 5 and 6, in the position to which it as been moved to carry out the step of the operation illustratedin Figure 7.

Fi ure 9 is a view similar to Fi ure 7, showing the vtube in the closed mol after the fourth step of my improved'method has beencarried out.

Figure 10 is a. view of the valve shown in the preceding figures, in the position it has been moved to carry out the step of my method illustrated in Figure 9.

Figure 11 is a view of said valve showing the position of the valve illustrated in the preceding figure, in the position it is moved immediately subsequent to the carrying out of the step of the method illustrated in Figure 9.

Figure 12 shows the tube mounted in the molding apparatus, where it is being subjected to the fifth step of my improved method and Figure 13 shows the tube in the mold aft-i er vulcanization, and after the concluding step of m improved method has been carried on with respect to said't ube.

Referring now to the drawings, wherein similar reference characters refer to similar parts throughout the several views, the reference numeral lindicates a tube of raw rubber, which has been produced in any suitable way, as for instance, by means of a tubing machine, and which has been cut to a suitable'length to produce a tube of the desired diameter. The ends of this tube of raw rubber are then brought together and united in any suitable way to produce the tube 2, a valve stem 3 having been inserted in the tube before the ends thereof were united. The manner of insertin the valve stem and splicing the endsof t e tube together form no part of the resent invention, although I prefer to utihzethe method disclosed in my co-pending application Serial Number 11,006, filed February 24th, 1925.

The reference numeral 4 denotes one section of a circular mold, having one part of the molding chamber illustrated at 5, said mold being preferably steam jacketed, the

steam chamber being indicated at 6. The

I section 4 has a laterally extending arm 7,

.to which is pivoted at 8 the upper section 9 perfect fit, whereby no part of the tube to be subjected to the vulcanizing process will be forced between the meeting edges of the sections of the mold.

At this point it may be noted that I prefer I to form the mold sections so that the greater part of the vulcanizing surfaces of the mold will be located in the lowermost mold section, asfillustr'ated in my pending ap lication, Serial Number 521,391, filed Decem er 10th, 1921. In other words, the mold is divided above its centre for a reason which will be a parent hereinafter. It will also be noted t at the.vulcanizing chamber of the mold is iven an oval cross-section, so that the finshed tube will have a like cross-sectional contour when the vulcanizing operation has been performed thereon.

The above described assembly'of mold sections is pivotally mounted at 12 upon a suitable supporting standard 13, so that said assembly may be swung to the various positions hereinafter to be described.

The reference numeral 14 illustrates a valvecas ing of a three-way valve 15, which may be operated as by means of the handle 16. Communicating with the valve chamber 14 is a conduit 17 which leads from a suitable source of exhaust, not shown, such for instance as a vacuum tank. Leading also into this valve casing 14 is a conduit 18 which extends from a source of fluid ressure, not shown, for instance, a tank lled with air. carbon dioxide, or other gas under pressure.

Leading from the valve casing 14'is a conduit 19 which extends through a valve casing 20, suitably mounted upon a vulcanizing alpparatus. A V-shaped passa away 21 in t e valve member 14 is ada te to connect either the vacuum conduit 1 with the conduit 19, or the fluid pressure conduit 18 with said conduit 19, the valve member 15 when moved to the position shown in Figure 3, being operative to shut off communication from both the vacuum conduit and the fluid piessure conduit from the conduit 19.

ading from'the valve casing 20 is a conduit 22, preferably flexible, which extends tion 4, as il heated fluid medium under pressure, which is suitable to be employed as a vulcanizing gas. In the present instance I have indicated the conduit 23 as leading from a source of steam pressure not shown. Located in the valve chamber 20 is a valve 24 having the V-shaped passageway 25. This valve member 24 may be so moved as to connect either the conduit 19 with the conduit 22, or the conduit 23 with the conduit 22, or to such a position as will shut off both conduits 19 and 23 from the conduit 22. In the present instance the valve 24 is provided wlth a laterally extending arm 26 adapted to be operated by means of a link 27 extending from the tiltable platform 28, upon which the lower section 4 of the mold is mounted, so that when the mold assembly is swung upon its pivotal axis 12 the valve 24 will be operated 1n a manner hereinafter to be described. 7

It will be understood, of course, that the mechanism illustrated in the drawing, employed for carrying out the various steps of my process is largely schematic, the preferred form of mechanism being illustrated in my application Serial Number 54,054, filed contemporaneously herewith.

Also it Wlll be understood that in practice means will be employed for locking the mold sections together and for suppl ing steam to the steam chambers 6 and 11 o the mold sections.

Referring now to the first step of my method, su sequent to the formation of the tube 2, and-the insertion of the valve stem 3, the latter is connected with a suitable source of vacuum to colla se the tube. This operation may be pre erably performed prior to depositing it in the lowermost secustrated in Figure 3. The conduit 22 is then connected with the valve stem 3, the collapsed tube occupying a position substantially as shown in Figure 3 of the drawings.

The valve 15 is then operated to connect the conduits 18 and 19, suflicient air being projected into the tube 2, resting in the valve chamber 5, to partially inflate the same, causing the outer wall of the raw rubber tube to engage with the heating surface of the lower mold section 4. At this int it may be noted that air. or other gas, orced in the tube of raw rubber, during this step of my mold, is relatively cool, so as to counteract the effect of the heated mold 4, and to prevent the raw rubber tube from collapsing within the heated section; and also to prevent the upper edge of the tube 2 from loppingover on the edge of the .mold section,

whereby it would be pinched in between the mating edges of the mold section when they are closed. The cold gas further retards the vulcanization of the tube for a short time, thus preventing the compound of raw rubber to be softened before the hardening process of vulcanization takes place. Only sufficient air is projected into the tube during this operation, to cause the same to take on a form substantially shown in Figure 4 of the drawings. The upper section 9 of the mold is then closed down on the lower section, whereupon the valve member 15, which was moved to a neutral position after the insertion of the initial air into the tube, is again moved to connect the tube with a source of air to expand it within the heatedmold, so that its outer wall will effect a close engagement with the vulcanizing surface of the mold chamber. When-this etc of the method has been accomplished, t e valve member 15 is then again operated to connect the inflated tube within the mold chamber with a source of vacuum through conduit 17 so that all air pressure within the tube will be removed; 'It is not intended, however, that sufficient suction will be applied to the .tube tocause it to become disengaged yyith the heating surface of the mold chamer. I

With reference to Figure 3it will be seen that when the mold section 4 is in a horizontal position, the valve member 24 has a partly open connection between the conduit 19 and the conduit 22, the operations above described having been. accomplished by manipulating the valve member 15 by its handle 16.

Having reduced the air pressure within the tube to sub-atmospheric pressure, the suction is then shut off and steam under pressure is'forced therein.v A convenient way of performing this step of the method is exemplified 1n the mechanism shown in the drawings, which step is accomplished by tilting the mold assembly upon its ivotal support 12 to vthe position shown in igure 12 of the drawings, which operation it will be noted, through the associated mechanism, will cause the valve'member 24 to shut of! communication between the conduit 19 and the conduit 22, and to establish connection between the conduit 22 and the conduit 23, which leads from the source of steam pressure. It will be understood, of course, that the mold sections have been heated to the vulcanizing temperature, and are intended to be constantly maintained at said temperature during. the vulcanizing operation upon a single tube, or upon successive tubes, as they are inserted in t e mold.

' The mold now being in the position shown in Figure 12, and connected with the source of steam pressure, the vulcanizing process is taking place, the length of time for which,

ofcourse, depends u on the nature of the raw rubber compoun ,of which the tube is composed, and the vulcanizing temperature of the mold, as well as of the heat of the steam or other vulcanizing gas being sup plied through the conduit 23.

When the vulcanization process has been completed, the mold assembly is tilted to the position shown in Figure 13, the valve member 15 having been moved tov a position to connect the conduit 19 with the vacuum conduit 17, so that when the parts occupy the position shown in Figure 13, thesteam and water of condensation within the vulcanized tube will be removed, and said vulcanized tube collapsed within the mold. When this operation has been accomplished, the valve member 15 will be moved to the neutral'position shown in Figurell, whereupon the mold will be moved to the horizontal position, the upper section moved to the position shown in Figure 3, whereupon the vulcanized tube 2 may be removed from the the tube and inserting the valve stem; (2nd) to collapse the tube and insert it in the mold section 4; (3rd with cold air or other gas; (4th) after completely enclosing it within the mold, to further inflate it with the cold air or other gas to expand it within the mold; (5th) to reduce the pressure of air or other cold gas to substantially a sub-atmospheric ressure;

(6th) project steam or other. vu canizing gas into the tube and maintain the internal pressure of the steam or vulcanizing gas within the tube durin the vulcanizing process; and (7th) after the vulcanizing process has been carried on, to remove the steam and water of condensation from the tube by a sucking operation, which last mentioned operation also collapses the tube within the mold, facilitating its ready removal when the mold sections are moved to their open position.

' While in the above description I have indicated that I refer to collapse the tube before insertin it into the lowermost section 4, itv will be 0 vious that this step of the method. may be performed after the unvulcanized tube has been inserted into said secpartially inflate it tion; and while I have illustrated certain of the steps of my method as being automaticall performed as by means of the tilting of t e mold to the position shown in Figure Y It will accordingly be seen that I'have provided a method of producing a pneumatic tube, which is well adapted to attain, among others, all the aims and objects of my invention, in a most eflicient manner. The tube produced according to my method is seamless and is of uniform thickness and texture. It is also free from wrinkles .upon its inner periphery. Moreover, the forming of the tube of elliptical or oval cross-section,

has the advantage that when the tube is in serted within a casingv and inflated, the inflating operation will cause the tube to errpand equally in all directions, whereby 1t will be of uniform thickness throughout its whole extent during service.

While I- have shown a preferred form of apparatus for carrying out the various steps employed in my method, it is obvious that other forms of apparatus may be employed for carrying out such steps without departing from the scope of the present invention.

It will be noted that the lower mold section is in a horizontal position when the unvulcanized tube is deposited therein. This 'ves further insurance against the soft ru ber compound, of which the tube is composed, softening. to such an extent that the up er edge of the tube will fall or lop over the e ge of said lower section, so that one or more parts thereof would be pinched between the mold sections when they are closed upon each other.

As many changes could be made in this construction without departing from the scope of the following claims, it is intended that all matter contamed in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not in a limiting sense.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is 1. The herein described method of producing a pneumatic tube, which consists in providing a tube of unvulcanized rubber compound, uniting the ends of said tube, withdrawing the air therefrom by suction, filling said tube with steam, and then vulcanizing said tube.

2. The herein described method of producing a pneumatic tube, which consists in providing a tube of unvulcanized rubber, inserting one end of said tube into the other end thereof to form a la ped splice, placing the tube in a closed mold heated to substan tially the vulcanizing temperature withdrawing air from said tube by suction, injecting steam under pressure into said tube, and permitting said heated medium to remain within said tubewhile it is being subjected to the vulcanizin process.

3. The iierein described method 'of producing a. pneumatic tube, which consists in providing a tube of unvulcanized rubber compound, splicing the ends of said tube, inserting a valve stem therein, placln said tube in a closed mold heated substantia ly to the vulcanizing temperature, forcing air into said tube through said valve stem to expand the tube within the mold, sucking the air from the tube through said valve stem, and then forcing steam under pressure through said valve stem into said tube, and maintainin g the pressure therein while the tube is being subjected to the vulcanizing process.

4. The herein described method of producing a. pneumatic tube, which consists in providing a tube of unvulcanized rubber compound, splicing the ends of said tube, inserting a valve stem therein, placing said tube in a closed mold heated substantially to the vulcanizing temperature, forcing air into said tube through said valve stem, to expand the tube within the mold, sucking air from the tube through said valve stem, forcing steam, under pressure into said tube, subjecting said tube to the vulcanizing process, and then sucking the steam and water condensation from said tube.

5. The herein described method of producing a pneumatic tube, which consists in pro viding a tube of unvulcanized rubber compound, splicing the ends of said tube, insertmg a valve stem therein, lacing said tube in a closed mold heated su stantially to the vulcanizing temperature, forcing air into said tube throu h said valve stem, to expand the tube within the mold, relieving thepressure within said tube by removing a quantity of air or other gas therefrom, forcing steam under jecting said tube to the vulcanizing process, and then sucking the steam and water condensation from said tube.

6. The herein described method of formin a pneumatic tube, which consists in providin a tube of unvulcanized rubber compoun uniting the ends of said tube, inserting a valve stem therein, placin said tube in one part of a circular mold heated substantially to the vulcanizing temperature, injecting air into said tube, placing the other heated section of the mold upon said first named section, whereby the tube is completely enclosed, injectin a further quantity of air into said tu e to expand the same within the-mold, sucking the air from said tube, injecting steam under pressure into said tube, permitting said tube with its enclosed steam to remain in said mold while being subjected to the vulcanizing process, then sucking the steam and water of condensation from said tube.

7. The herein described method of formin a pneumatic tube, which consists in provi ing a tube of unvulcanized rubber compound, uniting the ends of said tube, inserting a valve stem therein, placing said tube 1n one part of a circular mold heated sub pressure into said tube, sub-' stantially to the vulcanizing temperature, injecting air into said tube, lacing the other heated-section of the mold upon said first named section, whereby the tube is completely enclosed, injecting a further quantity of air into said tube to expand the same within the mold, sucking the air from said tube, injectingsteam under pressure into said tube, permitting said tube with its enclosed steam to remain in said mold while the tube is being subjected to the vulcanizing process, and then collapsing said tube within said mold b suction, whereby to free it from the mol and remove the steam and water of condensation.

8. The herein described process, which consists in providing a tube of unvulcanized rubber, bringing the ends of said tube together and forming said ends into a lapped union, inserting a valve stem into said tube, placing said tube in one part of an individual sectional mold heated to the vulcanizing temperature, injecting a quantity of relatively cold air into said tube, placing the other part of said section of said heated mold upon the first named section, whereby the tube is entirply enclosed by said mold sections, forcin a further quantity of relatively cold air 1nto said tube to expand the same within the mold, sucking said air from the tube, forcing steam under pressure into said tube while the same is being subjected to the vulcanizing temperature of the mold, sucking the steam and water of condensation from said tube after vulcanization, and then removing said tube from the mold.

9. The herein described method of formin a pneumatic tube, which consists in provi in a tube of unvulcanized rubber, uniting t e ends of said tube, inserting a valve stem therein, placin said tube in a closed mold heated to vlilcanizing tem erature, forcing relatively cool air into sai tube to ex and the same within the mold, sucking said air from the tube, forcing steam under pressure into said tube, allowing said steam under'pressure to remain in said tube during the vulcanizing process, sucking said steam and water of condensation from the tublei and then removing the tube from the mo 10. The herein described process for form- V ing a pneumatic tube, which consists in providing a tube of unvulcanized rubber, placing the ends of said tube in telescoping relation so as to form a lapped splice, inserting a valve stem therein, placing said tube in a closed mold, heated to the vulcanizing temperature withdrawing air from said tube by suction, forcing steam into said tube, and then maintaining a pressure of steam within said tube while thetube is being subjected to the vulcanizing process, whereby the tube is vulcanized and said lapped portions are formed into a homogeneous mass.

11. The herein described method of pro ducing a pneumatic tube, which consists in providing a tube of unvulcanized rubber compound, splicing the ends of said tube, inserting a valve stem therein, placing said tube in a closed mold heated substantially to the vulcanizing temperature, forcing cold air into said tube through said valve stem to expand the tube within the niold, sucking the air from the tube through said valve stem, and then forcing steam under pressure through said valve stem into said tube, and maintaining the pressure therein while the tube is being subjected to the vulcanizing process. p

12. The herein described method of formingla pneumatic tube, which consists in provi 'n a tube of unvulcanized rubber compoun uniting the ends of said tube, inserting a valve stem therein, placing said tube in one partof a circular mold heated substantially to the vulcanizing temperature, injecting cold air into said tube, placing the other heated section of the mold upon said first named section, whereby the tube is completely enclosed, injecting a further uantity of cold air into said tube to expan the same within the mold, sucking the air from said tube, injecting steam under pressure into said tube, permitting said tube with its enclosed steam to remain in said mold while being subjected to the vulcanizing process, then sucking the steam and water'condensation from said tube.

In testimony whereof, I aflix my signature.

WALTER L. FAIRCHILD. 

